The present invention relates to receive circuits and associated methods for minimizing channels in ultrasound imaging systems. In particular, circuits, controllers and methods for combining signals from multiple elements onto a same path are provided.
Medical diagnostic ultrasound imaging systems have a limited number of receive beamformer channels. The size of coaxial cables connecting transducer elements to the imaging system and associated receive beamformer channels may also limit the number of usable elements of a transducer array. To maximize the number of elements used, signals from a plurality of elements may be multiplexed onto a same cable. U.S. Pat. No. 5,573,001, the disclosure of which is incorporated herein by reference, discloses partial beamforming to combine signals from multiple elements for processing by a single receive beamformer channel. Signals from different elements are mixed with signals having selected phases, and the mixed signals are then summed together to form a partially beamformed sub-array signal. The subarray signal is responsive to each of the plurality of elements and may be processed with a single receive beamformer channel. Subarray mixing across an array allows the use of more elements than receive beamformer channels. Subarray mixing or partial beamforming may be desired in some situations and undesired in others. Multiplexing may be desired in some situations, but undesired in others. For example, multiplexing may not reduce the number of receive beamformer channels needed as compared to the number of elements.
The mismatch between the number of transducer elements and the number of receive beamformer channels or cables may occur in three-dimensional imaging systems using multi-dimensional arrays of transducer elements. Where the number of cables or receive beamformer channels is limited, circuitry may be provided within a transducer assembly for performing multiplexing or sub-array mixing. For example, U.S. Patent Nos. 2005-0148878 A1 and 2005-148873 A1, the disclosures of which are incorporated herein by reference, disclose detachable transducer probe assemblies providing one of multiplexing or subarray mixing.